I installed this quickly, and it already sits below the breadcrumb navigation. In the plugin file you can see the following also, which places it under the navigation:
$page=preg_replace('#<div class="navigation">(.*)</div>#Usi','<div class="navigation">$1</div><br />
<table border="0" cellspacing="'.$theme["borderwidth"].'" cellpadding="'.$theme["tablespace"].'" class="tborder">
<thead>
<tr>
<td class="thead" width="100" align="center"><strong>Latest '.
/* Use below code and set ^^(width) higher if you want board name to be said:
$mybb->settings['bbname']
*/
'news: </strong></td><td class="thead"><strong><marquee direction="left" scrollamount="5">'.$news.'</marquee></strong></td>
</tr>
</thead>
</table>',$page);
What goes around comes around